Lock-stitch sewing-machine.



No.7l5,9ll. f Patented Dec. I6, 1902.

G. E. WARREN.

LOCK STITCH SEWING MACHINE.

(Application filed Apr. 30, 1897.)

(No Model.)

WITNESSES. .INVENTOH w .y awaiw Wm A TTORNEYS'.

UNITED STATES PATENT OFFICE.

GEORGE ELMER WARREN, OF PAWTUCKET, RHODE ISLAND, ASSIGNOR TO V UNITED SHOE MACHINERY COMPANY, OF PATERSON, NEW JERSEY, A

CORPORATION OF NEW JERSEY.

LOCK-STITCH SEWING-MACHINE.

SPECIFICATION forming part of Letters Patent No. 715,911, dated December 16, 1902.

Application filed April 30, 1897.

To all whom it ntay concern:

Be it known that I, GEORGE ELMER WAR- REN, of Pawtucket, in the county of Provi dence and State of Rhode Island, have invented an Improved Lock-Stitch Sewing-Machine, of which the following isa specification, reference being bad to the accompanying drawings, in which- Figure 1 is an elevation of so much of a lock-stitch sewing-machine as is necessary to illustrate my invention. Fig. 2 is a partial elevation showing the finger about to pull off thread from the shuttle. Fig. 3 shows, on an enlarged scale,a tension for the sh little-thread which also looks the shuttle-thread except when the pull-off operates on the shuttlethread.

My invention consists in locating the lock that is, the extent to which the shuttle-thread is drawn into the Work-by regulating the amount of slack in the shuttle-thread and by a yielding pull on the needle-thread-that is to say, the stitch is set by tightening the needle-thread, which then extends as a loop through the work; but the shuttle-thread then extends from the work through that loop of'needle-thread to the shuttle, and. consequently the effect of Ihepull which tightens the needle-thread is to shorten the loop of 3c needle-thread which extends through the work, and as that loop of needle-thread is shortened it engages the shuttle-thread and pulls the shuttle-thread into the work until all the slack of the shuttle-thread is exhausted, and the tension of the shuttle-thread prevents the shuttle-thread from being drawn any farther into the needle-hole through the work, as during the latter part of the pull on the needle-thread it yields through its ten- 40 sion,so that it cannot draw the shuttle-thread any farther into the work.

In most lock-stitch sewing-machines the lock-stitch is set by tightening the needlethread when both needle-thread and shuttlethread are under the desired degree of tension, so that the proper setting of the lock stitch depends upon the relative adjustment of the two tensions; but in that class of lockstitch sewing-machines designed for heavy Serial No. 634,578. No model.)

work, such as boots and shoes and other leather-work, the slack needle-thread extends from a heavy tension device to the work when the needle-thread is tightened to set the stitch, so that the length of stroke of the means for tightening the needle-thread determines the location of the lock or the proper setting of the lock-stitch, for the shuttlethread is pulled into the Work as far as the adjustment of the take-up requires, and the location of the lock is determined by the adjustment of the take-up stroke, the pull of the take-up being unyielding. In the first class of machines referred to the length of stroke of the means for tightening the needie-thread must always be sufficient to pull the needle-thread through its tension, while in the second class that length of stroke must be so accurately adjusted that the lock will be properly located when the take-up or other tightening means has completed its stroke.

The machine shown in the drawings is of usual construction, except that I have added a shuttle-thread pull-off, which I have shown as a thread-finger A, mounted on a lever a, oscillated by the lever B and cam b and spring b. This intermediate lever B is used in order that the stroke of the finger A may be readily adjusted, as by adjusting the link o The shuttle D (and its operating mechanism, not shown) is as usual, except thatI use a much heavier tension on the shuttle-thread (1, so heavy, in fact, that it does not yield, except under the pullof the thread-finger A, by which shuttle-thread is pulled through the shuttle-tension. The preferred form of shuttle-tension is shown in Fig. 3, and this tension is a locking device for the shuttle-thread, except when the thread-finger A operates, for the friction of tension-springt on the shuttlethread, aided by the brake-spring t upon the go bobbin d, is great enough to prevent the yielding of the shuttle-thread, except under the action of the shuttle-thread pull-off.

The take-up F is as usual, except that its stroke is in excess of that required to set the lock-stitch instead of being accurately adjusted, as heretofore, so that at the end of its stroke it locates the lock by tightening the needle-thread g. The needle-thread tension G is also as usual, except that I have added a locking mechanism, shown as a ratchet on the tension, and a pawl g, which is caused to engage the ratchet, and thereby greatly increase the needle-thread tension just before the thread-finger A operates to pull off thread from the shuttle.

In Fig. 1 the thread-finger A, as shown in full lines, is just about to operate, and the pawl g is just about to be released by its cam 9 so that it will engage the ratchet on the tension before the thread-finger A engages the shuttle-thread d. The dotted lines in Fig. 1 show the thread-finger A pulling of? thread from the shuttle. The operation of this form of my invention is as follows: After a stitch is set and while both threads (1 and g are taut and the needle-thread 9 under its heavy tension finger A pulls thread from the shuttle,the length of shuttle-thread pulled 01f being suflicient for the next stitch. A new loop of needle-thread having been formed, the shuttle is carried through it and the needle-thread is tightened about the shuttlethread by the take-up F; but the lock is located when all the slack of the shuttle-thread is taken up, for when the take-up operates the pawl g is free from the ratchet on tension G and the needle-thread is under light tension until the take-up has completed its stroke, which is in excess of that required to take up all the slack of the needle-thread, and during the latter part or excess of the stroke of the take-up F the needle-thread renders through the take-up and through tension G-that is, the pull of the take-up on the needle-thread, while sufficient to tighten the needle-thread, and thereby cause it to pull the slack of the shuttle-thread into the needle-hole in the work, is not sufficient to pull the shuttle-thread any farther into the work than the slack of the shuttle-thread allows, for during the first portion of the movement of the take-up both needle-thread and shuttle-thread are slack; but after both are drawn taut by the action of the take-up the take-up mechanism makes its excess stroke with a yielding pull on the needle-thread, for the heavy tension of the shuttle-thread prevents any further motion of the needle-thread under the yielding pull of the take-up during its excess stroke. WVhen the take-up F has completed its stroke and set the stitch, the pawl of the locking mechanism engages the ratchet, increasing the tension on the needlethread, and the take-up dwells while the pulloif finger operates on the shuttle-thread (Z. The gist of the matter is keeping such a tension on the shuttle-thread thatit will not render through that tension before the take-up or other means for tightening the needlethread g has completed its stroke and causing the latter portion of the stroke of the take-up to give a yielding pull on the needlethread, and this necessitates some means for pulling off thread from the shuttle after the stitch is set and also necessitates in the best form of my invention some means for pulling 01f needle-thread as the stitch is set, for itis practically impossible to lock both needlethread and shuttle-thread at the moment the stitch is set, owing to the extreme nicety of adjustment of a take-up with a constant stroke, which would be necessary if both were then looked; but it is essential that one of the two threads be locked when the stitch is set in all lock-stitch machines for heavy work, and heretofore the needle-thread has always been then locked. I am the first to put heavy tension on the shuttle-thread and light tension on the needle-thread when the stitch is set in combination with means for pulling off the desired amount of shuttle thread, the main advantage being that the location of the lock is determined readily and with the nicest accuracy by simply adjusting the length of thread pulled ofi from the shuttle. Another advantage is that nice adjustment of the shuttle-thread tension is not required.

I am aware of the patents to Nason, No. 567,000, dated September 1, 1896, to Dial, No. 446,830, dated February 17, 1891, and to Diehl, No. 465,557, dated December 22, 1891, and I disclaim all shown in those patents.

I do not claim, broadly, a finger for pulling off thread from the shuttle, nor do I claim, broadly, holding the shuttle-thread against the pull of the take-up under such heavy tension that the shuttle-thread will not render through that tension; but I am the first to invent a sewing-machine with means to give the take-up mechanism a particular timing and with means for pulling 01f the proper amount of shuttle-thread, and thereby rendering it certain that the locks of the stitches will be located at a uniform distance from the surface of the work.

What I claim as my invention is A sewing-machine comprising a shuttle; a tension for the shuttle-thread; a tension for the needle-thread; a take-up mechanism for the needle-thread; means to give the take-up mechanism a stroke suificient to cause the needle-thread to render through its tension and to give the take-up a dwell at the end of the stroke; means to pull off thread from the shuttle while the take-up mechanism dwells; and means to lock the needle-thread against the pull of the shuttle-thread while the takeup mechanism dwells and while the shuttlethread is pulled ofi, all combined to produce the result above described.

GEORGE ELMER WARREN.

Witnesses:

A. L. GOODING, M. E. DALLOFF. 

